I really like this composition. It gives a wonderful comparison of size between the squirrel and the tree. This may have worked better in a vertical composition to emphasize that even more. Focus on the squirrel seems just a little bit soft. A little bit more DOF would probably help there. 8
The little guy is really cute, and he's very well placed in the frame. Unfortunately, there seems to be quite a heavy blue/cyan colour cast in the image.
Lovely composition and wonderful sense of scale provided by inclusion of so much tree. Great use of DOF to leave foreground tree and squirrel in focus and blur background trees - and really like that background is same colour palette as most of foreground rather than green or blue or such. Lovely detail.
Typically, wildlife shots at such a distance really lose their impact, but the gray layering of the trees' vertical lines with a curious splash of squirrel (looking rather skittish) has great visual effect. Were the entire foreground tree's bark in focus, the image might seem too flat.
This is an awesome capture. Love the mood - feel like I"m right there and have this cute little guy looking at me - love the way you framed it and composed it - wonderful use of rule of thirds. Creates more interest and drama the way you shot it.